1. Field of the Invention
This invention generally relates to portable heart monitors and particularly relates to transtelephonic heart monitors.
2. State of the Prior Art
Portable heart monitoring apparatus are well known to the art. Generally, such monitors analyze electrical activity of the heart as sensed by means of skin electrodes and generate an output signal in response thereto. The audio signal may be used either as a warning signal or to facilitate transmission of the derived information over telephone lines. Circuitry for accomplishing this function is disclosed in U.S. Pat. No. 3,742,483 issued to Stern and in U.S. Pat. No. 3,872,251 issued to Auerbach et al.
Acoustical monitoring of prosthetic heart valve function is relatively new to the art. Such a monitoring involves analyzing the acoustic characteristics of the functioning heart valve as sensed by means of a microphone placed upon the chest, over the heart, and generating an output signal in response thereto. Circuitry for accomplishing this function is disclosed in commonly assigned co-pending U.S. patent application Ser. No. 243,229, filed by Badzinski et al on Mar. 13, 1981 entitled "Monitoring System." At present, applicant knows of no such acoustical monitoring system suitable for in-home use by the patient.
Generally, portable heart monitors are provided with electrodes which are coupled to the monitors by means of cables, as illustrated in U.S. Pat. No. 3,991,747 issued to Stanly et al and in U.S. Pat. No. 3,934,507 issued to Sarnoff et al. This approach is inconvenient for the patient to use, and has a major drawback the problem of cable breakage, which can lead to inaccurate monitoring of cardiac function.
Recently, some portable heart monitors have incorporated electrodes attached directly to the monitor housing as in U.S. Pat. No. 3,547,107 issued to Chapman. These monitors have generally used metal electrodes, as in Chapman, which are subject to corrosion and oxidation which may act as insulative layers over the electrodes and interfere with their proper function over time. The "Cardiophone" monitor, illustrated on page 16 of Medical Electronics, June 1981, appears to use foam electrodes which, although immune to corrosion and oxidation, require regular moistening with electrode gel, a messy and time-consuming procedure. Application of an insufficient amount of gel can also interfere with proper functioning of the electrodes.